Re: [platform-swt-dev] Using Threads

["Steve Northover" <Steve_Northover@xxxxxxxxxx>]

Display.syncExec() does not start a thread, it just runs a runnable.
That's why you block.

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;

public class Test extends Thread {
      int counter = 0;
      Label label;
      boolean isRunning;
      Display display;

      public Test(Label label) {
            this.label = label;
            this.display = label.getDisplay ();
      }

      public void updateLabel() {
            display.syncExec(new Runnable () {
                  public void run () {
                        label.setText(String.valueOf(counter));
                  }
            });
      }

      public void run() {
            try {
                  while (isRunning) {
                        Thread.sleep(1000);
                        counter++;
                        updateLabel();
                  }
            } catch (InterruptedException e) {

            }
      }

      public static void main(String[] args) {
            Display display = new Display();
            Shell shell = new Shell(display);
            shell.setLayout(new FillLayout(SWT.VERTICAL));
            Label label = new Label(shell, SWT.NONE);

            Button start_pause = new Button(shell, SWT.CENTER);
            start_pause.setText("Start");
            final Test watch = new Test(label);

            start_pause.addListener(SWT.Selection, new Listener() {
                  public void handleEvent(Event event) {
                        if (!watch.isRunning) {
                              watch.isRunning = true;
                              watch.start();
                        } else {
                              watch.isRunning = false;
                        }
                  }
            });

            shell.pack();
            shell.setSize(177, 223);
            shell.open();
            try {
                  while (!shell.isDisposed()) {
                        if (!display.readAndDispatch())
                              display.sleep();
                  }
            } catch (Exception e) {
                  e.printStackTrace();
            }
            display.dispose();
      }
}



|---------+---------------------------------->
|         |           Minh Chiem             |
|         |           <minhchiem@xxxxxxxxxxxx|
|         |           >                      |
|         |           Sent by:               |
|         |           platform-swt-dev-admin@|
|         |           eclipse.org            |
|         |                                  |
|         |                                  |
|         |           05/29/2003 03:05 AM    |
|         |           Please respond to      |
|         |           platform-swt-dev       |
|         |                                  |
|---------+---------------------------------->
  >---------------------------------------------------------------------------------------------------------------------------|
  |                                                                                                                           |
  |       To:       platform-swt-dev@xxxxxxxxxxx                                                                              |
  |       cc:                                                                                                                 |
  |       Subject:  [platform-swt-dev] Using Threads                                                                          |
  |                                                                                                                           |
  >---------------------------------------------------------------------------------------------------------------------------|




I'm written a stopwatch class and I need to make use of Threads.
However, using the Display.asyncExec() method seems to block the UI.

Is this a bug????

here's a sample code which demostrates what i'm trying to do

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;

public class
Async
implements Runnable
{
    int counter = 0;
    Label label;
    boolean isRunning;

    public Async(Label label)
    {
       this.label = label;
    }

    public void
    updateLabel()
    {
       label.setText(String.valueOf(counter));
    }

    public void run()
    {
       try
       {
          while(isRunning)
          {
             Thread.sleep(1000);
             counter++;
             updateLabel();
          }
       }
       catch (InterruptedException e)
       {

       }
    }

    public static void main(String[] args)
    {
       Display display = new Display();
       Shell shell = new Shell(display);
       shell.setLayout(new FillLayout(SWT.VERTICAL));
       Label label = new Label(shell, SWT.NONE);

       Button start_pause = new Button(shell, SWT.CENTER);
       start_pause.setText("Start");
       final Async watch = new Async(label);

       start_pause.addListener(SWT.Selection, new Listener()
       {
          public void
          handleEvent(Event event)
          {
             if (!watch.isRunning)
             {
                watch.isRunning = true;
                Display.getCurrent().asyncExec(watch);
             }
             else
             {
                watch.isRunning = false;
             }
          }
       });

       shell.pack();
       shell.setSize(177, 223);
       shell.open();
       try
       {
          while (!shell.isDisposed()) {
             if (!display.readAndDispatch()) display.sleep ();
          }
       }
       catch (Exception e)
       {
          e.printStackTrace();
       }
       display.dispose();
    }
}

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